'image_default_link_type' filter does not work

Description

The image_default_link_type filter exists in includes/media.php so plugin authors can default the link added to uploaded media. Unfortunately while the filter does replace the default value in the link field, it is immediately overwritten via JavaScript in the handlers.js file with the individual user's saved preference.

I believe a patch needs to be added to the handlers.js file to skip modifying the Link URL field if it has already been prefilled via the filter.